Aid agencies and foreign governments have joined the effort to find the thousands still missing after Sunday's massive earthquake sent tidal waves crashing into coastal towns and beach resorts across southern Asia.

Hundreds of fishermen are missing off the south coast of India. Many were out in their boats early on Sunday when the waves hit.

The magnitude 9.0 earthquake struck under the Indian Ocean off the western Indonesian island of Sumatra. It generated a giant wall of water that sped across more than a thousand kilometers of sea.

Authorities in India have said there is little hope of finding survivors among the fishing fleets battered by the waves.

There has been similar devastation in Sri Lanka. Although 1,600 kilometers from the epicenter of the earthquake, the tsunamis, with nothing to slow them in the open ocean, struck with great ferocity and swept inland as far as two kilometers.

A large-scale search and rescue operation is underway along the southern and eastern coasts for survivors. Relief officials in Sri Lanka say thousands appear missing, including scores of foreign tourists on holiday.

In Thailand, the search is continuing for scuba divers and other tourists who are believed to have been swept out to sea from beaches on the island of Phuket.

An Australian boy with Down's Syndrome is among the missing in Phuket. He and his parents
were standing close to the surf when the tsunamis hit and separated them. His sobbing mother spoke to the Australia Broadcasting Corporation

"He was calling me. Then they just went. They just all went," she said.

Australian Prime Minister John Howard says those searching for missing friends and relatives have his country's sympathy.

"My message to them is that all Australians try as best they can to share your grief and your anxiety and we can only hope in each case there is good news," said Mr. Howard.

Some Australian travelers have already begun arriving home. Among them is Ed Weaver, who was on vacation with his wife in Phuket, Thailand, and who saw local hotels devastated.

"We went downstairs. We thought we'd drop in the Holiday Inn. It's no longer there. There's a jet ski in the main foyer. Took in the pool and there's a three-foot long shark swimming round the pool but there's people that were on the beach, they didn't come back," said Ed Weaver.

The earthquake sparked tidal surges that reached as far as Somalia in east Africa. In the Seychelles, nine people are reported missing when a two-meter surge struck.

Food, medicine and fresh water are desperately needed in many parts after the floods ripped away vital infrastructure. Aid agencies and foreign governments face a race to get the supplies in quickly, with officials warning that the spread of disease could heap more devastation on countries unable to cope with the disaster.